GDF2 and pulmonary arterial hypertension: The potential therapeutic role of BMP9 has also been explored in experimental studies, suggesting that treatment of BMPR2-deficient PAEC with BMP9 ameliorated the endothelial barrier and decreased apoptosis; and in rodent experimental PAH models BMP9 increased BMPR2 expression and downstream signaling, reversing the PAH phenotype [94].